I thought Id share info to you about the BMW standard stereo.
I ordered the premium in my x1 but bought for my partner the upgrade for his 328i for xmas. I opened the box and was impressed with what I saw. Looks like Ill have to help put the speakers in and will take pics of anyone is interested.
I got the http://www.bavariansoundwerks.com kit

I'm waiting to see what these guys offer for the X1. If they don't come up with something in the next few months I'll be looking at alternatives. I just have the base stereo. It isn't bad, but there is lots of room for improvement. But if you are not an audiophile you might be able to live with the base stereo for a long time. Just depends on what your stereo needs are.

From what I've heard and read, the Harman Kardon does improve treble quite a bit over the US standard "HiFi" option, but has a somewhat thumpy bass and doesn't do all that much for improving midrange.
But both the HiFi and Harman Kardon options are supposedly way better than the European default, "standard".

I really like the base stereo and think it's about as good (but different) than the fancy pants enhanced premium sound in my M3. The expensive M3 system seemingly only outshines our X1 at very high volume levels.